A Better Lure To Detect & Control an Avocado Pest

An Agricultural Research Service (ARS) entomologist has developed a new tool for Florida avocado producers increasingly concerned about a disease that is killing their trees. It’s a lure that makes it easier to detect and control the invasive pest that spreads the disease. It’s one of the tools designed to help combat the disease.

Laurel wilt disease was first detected in Miami-Dade County groves in 2012. Efforts by Paul Kendra and his colleagues to control laurel wilt have implications far beyond Florida’s $23-million avocado industry. The disease, which has spread to nine Southeastern States, could wipe out the $468-million avocado crop in California and the $1.2-billion avocado industry in Mexico if left unchecked. It also has nearly wiped out trees that were once major parts of coastal forests in the Southeast, including swampbay and redbay trees.

“Laurel wilt is causing significant damage in Florida, and it could easily spread to other States, so keeping it contained is a major priority,” says Kendra, who is based at the ARS Subtropical Horticulture Research Station in Miami, Florida.

The disease is spread by the redbay ambrosia beetle (RAB), which bores into the tree and deposits a fungus (Raffaelea lauricola), triggering a defensive response that blocks the flow of water to the upper tree and limbs. Once infected, a tree can wilt and die within 2 months. To limit spread of the disease, avocado growers promptly remove the infected trees and inject the surrounding trees with a fungicide. Growers in Miami-Dade County have removed more than 12,000 infected trees during the past 3 years.

The Florida Department of Agriculture now monitors for RAB with traps containing cubeb oil lures. But Kendra and his commercial partner, Synergy Semiochemicals Corporation, based in British Columbia, Canada, have developed an improved lure that emits higher levels of a key attractant. The compound, known as a-copaene, is found in the wood of avocado and other laurel trees and is believed to be an important ingredient in the bouquet of compounds that the beetle uses to find host trees. Kendra and his colleagues distilled cubeb oil, separating out its chemical compounds for analysis, and exposed RAB to some of the most promising compounds to determine which ones were the most attractive. Based on their results, they developed two prototype lures, and then compared how well the two prototypes and the current cubeb lure attracted RABs during a 3-month field trial.

The experimental lure with 50 percent a-copaene captured two to three times more beetles and could detect beetles even when they were at very low numbers in avocado groves. The “high octane” lure also attracted RABs for the entire 3-month trial. Results were published in the Journal of Pest Science in December 2015.

Synergy Semiochemicals is now producing the new lure for forestry and agricultural use.—By Dennis O'Brien, ARS Office of Communications.

“A Better Lure To Detect & Control an Avocado Pest" was published in the November 2016 issue of AgResearch Magazine.